Byrne's Standard Website for Pool and Billiards

Chapter 3
Sidespin: the Pluses and Perils

Sidespin also affects the angle the cueball takes off the cuetip (squirt), the direction the object ball takes after the spinning cueball hits it (throw), and, if the cue isn't precisely level, the straightness of the path the cueball takes to the object ball (swerve). Because of squirt, throw, and swerve, it is much harder to be precise in aiming and pocketing balls when English is used as opposed to centerball hits. Top players have an uncanny ability to balance and exploit the three variables.

Players differ in their estimates of how many shots require hitting the cueball right or left of the vertical axis, but it is certainly much less than half. On the great majority of shots in pool, the cueball can be controlled adequately with centerball hits by varying the speed and by cheating the pocket.

REBOUND
One way learn how to judge the effect of sidespin on cushion rebound angles is practice banking drills. Here's one. Freeze balls along the long rails at each diamond. (Omit the two diamonds closest to the foot rail--the rail at the far end of the table.) Place the cueball on the head spot and shoot it straight down the center of the table to the center of the foot rail. (The head spot is not marked on most tables. It is on the centerline two diamonds from the head rail.) The challenge is to use just enough English to bounce off the center of the foot rail and hit any desired ball. Maximum sidespin and slow speed is required to hit the ball frozen to the side rail at the third diamond from the foot rail. Beginners usually can't do it. Drills like this get boring fast, so its best to practice them as competitive games with a friend.

THROW
When learning cut shots, students are usually told to try to make the cueball hit the spot on the object ball exactly opposite the pocket. That is correct advice if throw is ignored. Throw is the term used to describe the way the object ball is pushed off line by the friction between it and the cueball at the moment of impact. For maximum precision, the point that must be hit on the object ball changes with the amount of spin on the cueball. To gain an appreciation of the concept, put a ball in the center of the table and put the cueball about a foot away from it so you have a straight-in shot into a corner pocket. Aim straight at the object ball but with heavy right English. Pull the trigger and you'll see that the object ball is thrown to the left of the corner pocket. The reason is that when you apply right sidespin, the leading edge of the cueball is moving to the left, and when that moving surface hits the object ball, it "grabs" and throws it off line to the left. The same explanation applies to the way a frozen two-ball combination is thrown off line depending on how it is struck.

Throw occurs on cut shots also but is difficult to see. If you are cutting an object ball to the left, left-hand sidespin will require a slightly thinner hit than you would need if no sidespin were used. Right-hand spin will throw the object ball to the left, so a slightly thicker hit is required. Throw occurs on cut shots even if no English is used because the surface of the cueball rubs against the object ball and throws it off line. For a fuller discussion complete with diagrams, see Byrne's Advanced Technique, pages 23-27.

Because of the throw effect, it's a lot harder to pocket a ball when English is used. To drive the point home and convince you not to use English unless absolutely necessary, set up another straight-in shot with the object ball in the center of the table--this time put the cueball three or four feet away from it. Try to make the shot with heavy left or right English. You'll see how difficult it is. If you can make a long straight shot half the time with no English, you'll be lucky to make it one time in five with English. The loss of accuracy is partly because of throw and partly because of squirt.

SQUIRT
Another factor that makes English dangerous is deflection, now usually called squirt. When you hit a cueball right or left of center, it won't travel in a direction exactly parallel to the cue, it will diverge slightly in a direction opposite of the English. To see it for yourself, put the cueball on the headspot and aim directly at the center of the far rail with heavy right English. The cueball will hit the end rail to the left of the center point. Opinions differ on why some cues cause more squirt than others. In my opinion, to key factors are stiffness of the shaft (stiffness reduces squirt) and weight near the tip. Cues that have small diameter tips but are not too flexible cause less squirt than fatter cues, apparently because there is less weight near the tip. A cue that is front-heavy forces the cueball to one side at impact, while a cue that is front-light is pushed aside by the cueball. Whether this reasoning is correct should soon be known for sure, thanks to experiments that are now being conducted with high-speed cameras by two cuemakers, Predator and Meucci. Both have built ball-striking machines to eliminate human error. There may soon be answers to questions that analysts have been arguing about for years.

SWERVE
A third factor that makes it harder to pocket balls when English is used is swerve. Unless the cue is exactly level, English will make the cueball's path bend slightly. The more you elevate the back of the cue, the more the cueball will curve, or swerve. Because the cue is usually elevated at least slightly (the butt must clear the rail), swerve must be considered when English is applied. There are of course situations when swerve is needed to bend the cueball around an interfering ball.

CONCLUSION
Use English as seldom as possible. When you do use it, use as little as possible. Hitting the cueball a full half inch off center not only brings squirt, throw, and swerve into play, it increases the risk of a miscue. A quarter inch off center is usually plenty.